The objective of this study is to determine various parameters of cellular proliferation, life span, and migration patterns in leukemic, normal, and other selected individuals with various hematologic diseases affecting leukocytes. The information is sought to aid in the planning of therapy in leukemia. Cells will be labeled with various radioisotopes, including H3-thymidine, H3-DFP, and Cr51 in order to study various aspects of cellular proliferation and behavior. Attempts will also be made to grow human bone marrow cells in mice.